Glass-Lined Flange Joint Assembly With Fire-Rated Gasket Seal
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Solution Overview
Problem
Conventional glass-lined flanged fittings fail to meet the NFPA 30 standard for flammable and combustible liquids and do not pass the fire test specified in API Specification 6FB, particularly when connected to non-metal lined equipment.
Innovation Solution
A flanged fitting design featuring a glass liner on the radially inner annular portion of the flange and a fire-rated annular inlay on the radially outer portion, combined with a dual-layer gasket configuration using ePTFE and flexible graphite, to form a liquid-tight and fire-rated seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a glass liner is used to line the entire flange face, then corrosion resistance is improved, but fire rating is worsened (fails NFPA 30 and API 6FB fire tests)
Solution Approach 1:
The flange face is segmented into two distinct zones: a radially inner annular portion lined with corrosion-resistant material (glass liner) and a radially outer annular portion left as fire-rated metal. This segmentation allows each zone to fulfill its specific function - the inner zone provides corrosion resistance where it contacts the process fluid, while the outer zone provides fire rating for the seal interface.
Solution Approach 2:
Different materials and properties are applied to different locations on the flange face. The radially inner annular portion has corrosion-resistant glass liner coverage, while the radially outer annular portion maintains fire-rated metal properties. This local differentiation resolves the contradiction by providing both corrosion resistance and fire rating in appropriate locations.
2Device complexity
If a single-layer gasket is used, then device complexity is reduced, but sealing performance is worsened (cannot provide both liquid-tight and fire-rated seal)
Solution Approach 1:
The gasket is segmented into two functional layers: an inner layer that provides liquid-tight sealing against the glass-lined surface and an outer layer that provides fire-rated sealing against the metal flange face. This segmentation enables the single gasket component to deliver dual sealing functions that would be impossible with a single-material gasket.
Solution Approach 2:
The gasket uses composite construction with different materials optimized for different functions - the inner layer material is selected for chemical compatibility and liquid sealing, while the outer layer material is selected for fire resistance. This composite approach allows one gasket to satisfy both sealing requirements.
Data Source
AI summary
A flanged fitting includes an annular fitting flange having an annular end face. A glass liner lines a radially inner annular portion of the annular end face of the annular fitting flange. A radially outer annular portion of the annular end face of the annular fitting flange is free from the glass liner. The radially inner annular portion and the radially outer annular portion of the annular end face of the annular fitting flange define an annular gasket abutment face configured to seat a gasket thereon. An annular gasket includes an annular gasket layer. The annular gasket layer includes a radially inner annular gasket segment including a first material suitable for forming a liquid-tight seal with an opposing flange. A radially outer annular gasket segment surrounds the radially inner annular gasket segment. The radially outer annular gasket segment is fire-rated for forming a fire-rated seal with the opposing flange.